Gtr Air Chopping

[Cooper]

When my R33 GTR comes on boost you can hear the air being sucked in obviously but it sounds as if it is cutting in and out and is making a chopping sound while accelarating on boost. Does anyone have any ideas on what it could be? and is it bad?

The car does not stutter while it is doing this either. My car is standard but the boost restrictors have been taken out.

Any help would be appreciated.

Cheers

Edited July 26, 2006 by Cooper

[TTT]

Called compressor surge.

Search for it and sift your way through the flutter threads, and you will find explanation of this and possible solutions.

I’ve heard having aftermarket bovs on a gtr sometimes causes this.

Stock gtr bovs plumbed back as is from factory seems to fix issue.

If you have stock bovs already, then I’m stumped.

cheers

[paulr33]

it could be one of two problems you are seeing. the first one is compressor chuffing or shuffling, where you can hear compressor surging at idle and low rpm, it sounds like talking into back of a fan or a vl turbo style flutter between each of the turbo's. this is commonly associated (that we've seen) with bov changes and/or custom intake piping.

the other one that comes to mind is compressor wheel chopping. my gtst does this. as its coming on boost you can hear like a slicing noise, a bit like a hi speed food processor in coleslaw mode. ive had this since day 0 and a few other gtst have this same behaviour. i dont think its a problem, just an induction noise based on the compressor wheel

[FOG35]

I had this same problem with my rb20det. Does it while i accelerate between 3000-4000rpm and more often in a higher gear (etc 5th gear on the highway). I have a adjustment nut on my internal wastgate arm which allows me to turn the boost up without a boostcontroller. What i did was loosen the nut back to standard boost and the problem was fixed. To whether i have a faulty wastegate actuator, ecu cannot handle the amount of psi (11spi) or my turbo is f*cked im not sure. I think that the wastegate is flapping open and closed therefore causing a sudden loss of pressure in the exhaust wheel causing the turbo wheel slow down and the presure built up in the intercooler piping blows back out the turbo (flutter). It is hard to explain.

If anyone else has these problems please post.

[Cooper]

Thanks for replies, i have stock bov infact the car is completely standard, i hope its just a normal occurance. Cheers for the help i will have a look and sift thought the annoying flutter threads.

[R31Nismoid]

are the BOVs working? Not blocked/stuffed? Vacum lines connected etc?

[Cooper]

^^^ I am pretty sure the BOVs are working but saying that im not 100% i might have to take them off on the weekend and check them out, all the hoses and lines are all connected, as far as i can see anyway. Is there an easy way to get to the BOVs so that i can check them out?

[FOG35]

I dont see how it would have anything to do with the BOV. You say that it happens when you are accelerating (ie throttle body is open).

I think ^^^people above are getting mixed up with the flutter noise that happens when take your foot off the accelerator. If that is your problem then i would suggest checking your BOVs.

Pull off your intake pipes and see if there is any shaft play in either of the turbos.

[Cooper]

Yes its while accelerating on boost not flutter off boost, i will see if there is any shaft play on the weekend.

Thats for the replies